Fluorimeters using PMT detectors have been provided in the past, for more or less predictable, minimally varying light levels. In these and all detectors using PMT's, care is required that the light exposure not be so great as to swamp out the upper limit of detectability, since otherwise the PMT either a) takes far too long to "recover", and/or b) is permanently damaged. However, when the light level is not expected to vary much, or is based on a light source emitting at a constant output level, the PMT is not in jeopardy.
A field of use has arisen that does jeopardize the PMT detector. Homogeneous PCR relies in many instances on fluorescence markers whose output is a function of the replicated concentration of the target DNA, which in turn is a function of the starting concentration. As a result, the marker concentration at time of detection can vary by a factor of 100 or more. Stated in other words, usage is possible wherein the fluorophore concentration is much higher than is expected for a given flashlamp intensity, and the PMT is "blinded".